In one type of a video projection system, a beam of light is projected onto means for modulating the light in accordance with a video signal. The modulated light beam is then directed through a projection lens onto a video screen. For a color projection system, the light source is split into its three color components, i.e., red, blue and green. Each color component of the light beam is then individually modulated. The three modulated components are then directed simultaneously through the projection lens and onto the screen.
One type of light modulator is a light valve having a blazed surface. A blazed surface is a surface made up of a plurality of small surfaces each at an angle less than ninety degrees with respect to the axis of the device. Also, the light valve includes means for selectively reflecting the light beam impinging on the blazed surface to the projection lens, or directing the light away from the projection lens so as to modulate the light. A type of light valve which has been developed for this purpose is a deformable mirror device which is formed of a plurality of mirrors which can be simultaneously pivoted to change the angle of deflection of light impinging on the mirrors. With a light valve having a blazed surface, the light from the light source is directed onto the blazed surface and is reflected from the blazed surface to the projection lens. Thus, the system heretofore used had the means for directing the light onto the light valve surface and the projection lens at the same side of the light valve, i.e., the side having the blazed surface. To permit the incoming beam of light and the outgoing beam of light from interfering with each other, it has been necessary to provide a relatively large space between the light valve and each of the means for directing the light beam onto the light valve and the projection lens. This is particularly true for color projection systems which have three separate light valves, one for each color. In order to make the projection system more compact, it is desirable to have a system in which the light directing means and the projection lens can be placed as close as possible to the light valve and still not have interference between the incoming and outgoing light beams.